1. Field of the Invention
One or more embodiments of the present invention relate to audio coding, and more particularly, to a method, medium, and system generating a 3-dimensional (3D) signal in a decoder by using a surround data stream.
2. Description of the Related Art
FIG. 1 illustrates a conventional apparatus for generating a stereo signal. Here, a quadrature mirror filter (QMF) analysis filterbank 100 receives an input of a downmixed signal and transforms the time domain signal to the QMF domain. The downmixed signal is a signal that previous to encoding included one or more additional signals/channels, but which now represents all of the signals/channels with less signals/channels. An upmixing would be the conversion or expanding the downmixed signals/channels into a multi-channel signal, e.g., similar to its original channel form previous to encoding. Thus, after transforming of the time domain signal to the QMF domain, a surround decoding unit 110 decodes the downmixed signal, to thereby upmix the signal. A QMF synthesis filterbank 120 then inverse transforms the resultant multi-channel signal in the QMF domain to the time domain. A Fourier transform unit 130 further applies a faster Fourier transform (FFT) to this resultant time domain multi-channel signal. A binaural processing unit 140 then downmixes the resultant frequency domain multi-channel signal, transformed to the frequency domain in the Fourier transform unit 130, by applying a head related transfer function (HRTF) to the signal, to generate a corresponding stereo signal with only two channels based on the multi-channel signal. Thereafter, an inverse Fourier transform unit 150 inverse transforms the frequency domain stereo signal to the time domain.
Again, surround decoding unit 110 processes an input signal in the QMF domain, while the HRTF function is generally applied in the frequency domain in the binaural processing unit 140. Since the surround decoding unit 110 and the binaural processing unit 140 operate in different respective domains, the input downmix signal must be transformed to the QMF domain and processed in the surround decoding unit 110, and then, the signal must be inverse transformed to the time domain, and then, again transformed to the frequency domain. Only then, is an HRFT applied to the signal in the binaural processing unit, followed by the inverse transforming of the signal to the time domain. Accordingly, since transform and inverse transform are separately performed with respect to each of the QMF domain and the frequency domain, when decoding is performed in a decoder, the complexity increases. With such complexity, such an arrangement may not be suitable for a mobile environment, for example. In addition to the complexity, sound quality is also degraded in the processes of transforming or inverse transforming a domain representation, such as transforming a QMF domain representation to a time domain representation, transforming a time domain representation to a frequency domain representation, and inverse transforming a frequency domain representation to a time domain representation.